South Korea's new coronavirus cases dipped to more than a month low Thursday as imported cases dwindled from last week's record high over infections traced to the virus-hit Iraq and Russian sailors.

The country added 18 cases, including 11 imported cases, raising the total caseload to 14,269, according to the Korea Centers for Disease Control and Prevention (KCDC).

The tally marked a sharp decline from 48 new virus cases reported Wednesday and 28 cases Tuesday.

It also marked the lowest since June 22 when the number of new daily cases hit 17.

The country's imported cases have recently surged as infections spiked among South Korean workers returning home from Iraq and Russian sailors. Imported cases, which hit a record 86 on Saturday, have risen by double-digit numbers for 35 straight days.

Of the newly reported imported cases, four cases were from the Philippines, followed by Saudi Arabia with three and the United States with two. The total caseload of cases coming in from overseas reached 2,374. 

Infections traced to Russian ships docked in South Korean ports have become a new source of cluster infections here since last month, with the number of related cases hitting 91 so far.

An additional 12 sailors aboard a ship docked in the southeastern port city of Busan tested positive for the virus Wednesday, raising the number of related infections to 44.

In addition, one Russian sailor aboard a cargo ship docked in Incheon, west of Seoul, was also confirmed to have contracted the virus.

Starting Monday, sailors aboard ships departing from Russia will be required to submit a certificate showing they have tested negative for COVID-19 as cluster infections tied to Russian ships have continued to swell.

Arrivals from six high-risk countries -- Bangladesh, Pakistan, Kazakhstan, Kyrgyzstan, the Philippines and Uzbekistan -- are required to submit coronavirus-free certificates.

"Starting today, South Korea began onboard quarantine inspections on not only ships from Russia but also vessels departing from the six countries," KCDC Deputy Director Kwon Joon-wook said in a press briefing.

Since early this month, South Korea has launched onboard quarantine inspections for vessels coming from Russia. The stricter checks were conducted on 74 percent of a total of 259 Russia-flagged ships arriving here this month.

At least 121 South Korean workers returning from Iraq have been confirmed to have been infected with the virus. Of some 290 people who returned home Friday, 77 workers have tested positive for the virus.

South Korea brought home hundreds of nationals from virus-hit Iraq twice in July and another 70 workers will come back home Friday.

Meanwhile, the country reported seven local infections, with three cases in Seoul and four in Gyeonggi Province that surrounds the capital.

Cases traced to a day care center for senior citizens in western Seoul reached 29 as of noon, up one case from the previous day.

Of six families who went camping together in the eastern city of Hongcheon, six people tested positive for the virus.

"We cannot lower our guards against the virus even at outdoor places, including beaches, mountains and camping sites. Cluster infections tied to camping can evolve into other cases during summer vacations," Kwon said.

Meanwhile, the KCDC said it will conduct virus tests on eight more people who had come in contact with a North Korean defector who has recently fled back to his communist homeland.

North Korea claimed the defector returned to the North on July 19 with suspected virus symptoms, but South Korea said he had neither tested positive for the coronavirus nor come into contact with confirmed patients.

The virus was not detected in 16 kinds of his belongings that were later found in the South after he has swum across the inter-Korean border.

Kwon said there is a "very low" possibility for the defector being infected with the virus but needs to be watchful due to a 14-day incubation period.

The country reported no additional deaths, with the death toll remaining at 230, according to the KCDC. The fatality rate reached 2.1 percent.

The number of patients fully cured of the virus reached 13,132, up 63 from the previous day.

South Korea has carried out 1,556,215 tests since Jan. 3. (Yonhap)